'Field required a bean of type that could not

问题:

So I've been learning Spring in the couples of week, been following this tutorial

Building a RESTful Web Service

All was well until I tried to integrate it to mongodb. So I follow this tutorial.

Accessing Data with MongoDB

But my practice is partially still using the first one. So my project directory structure is like this.

src/
├── main/
│   └── java/
|       ├── model/
|       |   └── User.java
|       ├── rest/
|       |   ├── Application.java
|       |   ├── IndexController.java
|       |   └── UsersController.java
|       └── service/
|           └── UserService.java
└── resources/
    └── application.properties

This is my model/User.java file

package main.java.model;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document(collection="user")
public class User {

    private int age;
    private String country; 
    @Id
    private String id;
    private String name;


    public User() {
        super();
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getCountry() {
        return country;
    }

    public void setCountry(String country) {
        this.country = country;
    }
}

This is my rest/UsersController.java file

package main.java.rest;

import java.util.List;
import main.java.service.UserService;
import main.java.model.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping(value = "/users")
public class UsersController {

    @Autowired
    UserService userService;

    @RequestMapping(method = RequestMethod.GET)
    public List<User> getAllUsers() {
        return userService.findAll();
    }
}

This is my service/UserService.java file

package main.java.service;

import java.util.List;
import main.java.model.User;
import org.springframework.data.mongodb.repository.MongoRepository;

public interface UserService extends MongoRepository<User, String> {
    public List<User> findAll();
}

I could compile them (I'm using gradle for compilation because I'm following the tutorial), but when I run the jar file it was throwing this error.

---

APPLICATION FAILED TO START

---

Description:

Field userService in main.java.rest.UsersController required a bean of type 'main.java.service.UserService' that could not be found.

Action:

Consider defining a bean of type 'main.java.service.UserService' in your configuration.

Not sure what is wrong I start googling around and found that I need to include Beans.xml file and register the userService in it. I did that but it's not working. I'm really new to this so I really have no clue on what's going on.

回答1:

Solved it. So by default, all packages that falls under @SpringBootApplication declaration will be scanned.

Assuming my main class ExampleApplication that has @SpringBootApplication declaration is declared inside com.example.something, then all components that falls under com.example.something is scanned while com.example.applicant will not be scanned.

So, there are two ways to do it based on this question. Use

@SpringBootApplication(scanBasePackages={
"com.example.something", "com.example.application"})

That way, the application will scan all the specified components, but I think what if the scale were getting bigger ?

So I use the second approach, by restructuring my packages and it worked ! Now my packages structure became like this.

src/
├── main/
│   └── java/
|       ├── com.example/
|       |   └── Application.java
|       ├── com.example.model/
|       |   └── User.java
|       ├── com.example.controller/
|       |   ├── IndexController.java
|       |   └── UsersController.java
|       └── com.example.service/
|           └── UserService.java
└── resources/
    └── application.properties

回答2:

Add the @Service in the service/UserService.java.

回答3:

I also had the same error:

***************************
APPLICATION FAILED TO START
***************************

Description:

Field repository in com.kalsym.next.gen.campaign.controller.CampaignController required a bean of type 'com.kalsym.next.gen.campaign.data.CustomerRepository' that could not be found.


Action:

Consider defining a bean of type 'com.kalsym.next.gen.campaign.data.CustomerRepository' in your configuration.de here

And my packages were constructed in the same way as mentioned in the accepted answer. I fixed my issue by adding EnableMongoRepositories annotation in the main class like this:

@SpringBootApplication
@EnableMongoRepositories(basePackageClasses = CustomerRepository.class)
public class CampaignAPI {

    public static void main(String[] args) {
        SpringApplication.run(CampaignAPI.class, args);
    }
}

回答4:

I encountered the same issue and all I had to do was to place the Application in a package one level higher than the service, dao and domain packages.

回答5:

Spent a lot of time because of the auto-import. Intellij Idea somewhy imported @Service from import org.jvnet.hk2.annotations.Service; instead of import org.springframework.stereotype.Service;!

回答6:

This thread is old now but I am posting my answer, which may be useful for others.

I had the same issue. It turned out that there is another class with the same name in other module. I renamed that class and it solved the issue.

回答7:

Add the @Component in your controller class. May this work

回答8:

Normally we can solve this problem in two aspects:

1. proper annotation should be used for Spring Boot scanning the bean, like @Component;
2. the scanning path will include the classes just as all others mentioned above.

By the way, there is a very good explanation for the difference among @Component, @Repository, @Service, and @Controller.

回答9:

I have same Issue, fixed by Adding @EnableMongoRepositories("in.topthree.util")

package in.topthree.core;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.data.mongodb.repository.config.EnableMongoRepositories;

import in.topthree.util.Student;

@SpringBootApplication
@EnableMongoRepositories("in.topthree.util")
public class Run implements CommandLineRunner {

    public static void main(String[] args) {
        SpringApplication.run(Run.class, args);
        System.out.println("Run");
    }

    @Autowired
    private Process pr;

    @Override
    public void run(String... args) throws Exception {
        pr.saveDB(new Student("Testing", "FB"));
        System.exit(0);
    }

}

And My Repository

 package in.topthree.util;

    import org.springframework.data.mongodb.repository.MongoRepository;

    public interface StudentMongo extends MongoRepository<Student, Integer> {

        public Student findByUrl(String url);
    }

Now Its Working

回答10:

In my case i have just put the Class MyprojectApplication in a package(com.example.start) with the same level of model, controller,service packages.

回答11:

In my case, I accidentally defined the service class abstract while doing copy and paste.

@Serivce
@Valdiated
public abstract class MyService { // remove the abstract modifier!!!
}

回答12:

My Mapper implementation classes in my target folder had been deleted, so my Mapper interfaces had no implementation classes anymore. Thus I got the same error Field *** required a bean of type ***Mapper that could not be found.

I simply had to regenerate my mappers implementations with maven, and refresh the project...

回答13:

I have come to this post looking for help while using Spring Webflux with Mongo Repository.

My error was similar to owner

Field usersRepository in foobar.UsersService required
a bean of type 'foobar.UsersRepository' that could not be found.

As I was working before with Spring MVC I was surprised by this error.

Because finding help was not so obvious I'm putting answer to this question as it is somehow related and this question is high in search results.

First thing is you must remember about what was mentioned in answer marked as accepted - package hierarchy.

Second important thing is that if you use Webflux you need to use some different package while when using Spring MVC e.g. for MongoDB you need to add

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
</dependency>

with -reactive at the end.

回答14:

Using this solved my issue.

@SpringBootApplication(scanBasePackages={"com.example.something", "com.example.application"})

回答15:

This may happen when two beans have same names.

Module1Beans.java：

@Configuration
public class Module1Beans {
    @Bean
    public GoogleAPI retrofitService(){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://www.google.com/")
                .addConverterFactory(JacksonConverterFactory.create())
                .build();
        return retrofit.create(GoogleAPI.class);
    }
}

Module2Beans.java：

@Configuration
public class Module2Beans {
    @Bean
    public GithubAPI retrofitService(){
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://www.github.com/")
                .addConverterFactory(JacksonConverterFactory.create())
                .build();
        return retrofit.create(GithubAPI.class);
    }
}

A bean named retrofitService is first created, and it's type is GoogleAPI, then covered by a GithubAPI becauce they're both created by a retrofitService() method. Now when you @Autowired a GoogleAPI you'll get a message like Field googleAPI in com.example.GoogleService required a bean of type 'com.example.rest.GoogleAPI' that could not be found.